US President Donald Trump told The New York Times in an interview Wednesday that he never would have appointed Jeff Sessions as attorney general had he known Sessions would recuse himself from overseeing the Russia investigation.

In an extraordinary denunciation of one of his earliest backers in Washington, Trump said Sessions’ decision to recuse himself from all matters related to Russia was “very unfair to the president”.

“Sessions should have never recused himself,” Trump told the paper, “and if he was going to recuse himself he should have told me before he took the job and I would have picked somebody else.”

He continued: ““How do you take a job and then recuse yourself? If he would have recused himself before the job, I would have said, ‘Thanks, Jeff, but I’m not going to take you’.”

If he was going to recuse himself he should have told me before he took the job and I would have picked somebody else

Donald Trump on his Attorney General, Jeff Sessions

Sessions’ recusal, announced following revelations that he had failed to disclose meetings with Russia’s ambassador to the US, effectively paved the way for the appointment of Robert Mueller as special counsel. Mueller’s investigation into Russian meddling in the 2016 election and potential ties between the Russian government and Trump campaign aides has cast a growing cloud on Trump’s administration.

In the interview, Trump also appeared to threaten Mueller, suggesting he had damaging information on the former FBI director.

Trump said Mueller’s selection for the job was a conflict of interest because Trump had interviewed him to serve as the replacement FBI director.

“He was up here and he wanted the job,” Mr. Trump said. After he was named special counsel, “I said, ‘What the hell is this all about?’ Talk about conflicts. But he was interviewing for the job. There were many other conflicts that I haven’t said, but I will at some point.”

He lobbed similar conflict of interest charges at acting FBI Director Andrew McCabe and Deputy Attorney General Rod Rosenstein, and accused former FBI director James Comey of briefing him on a dossier of unverified, incriminating information in an effort to gain leverage over the soon-to-be president.

Trump expressed annoyance aabout Rosenstein - who appointed Mueller as special counsel - when he learned that Rosenstein was from Baltimore, where he had served as a federal prosecutor.

“There are very few Republicans in Baltimore, if any,” Trump said.

The Justice Department declined to comment on the interview.

Trump also addressed the previously undisclosed conversation he had with Russian President Vladimir Putin during a dinner for world leaders at a summit in Germany.

Trump said the pair spoke for about 15 minutes at the dinner and said the conversation consisted mostly of “pleasantries” — though he said he and Putin also discussed “adoptions”.

Russia had banned Americans from adopting Russian children in response to t US sanctions against Russians deemed to be human rights violators.

“The meal was going toward dessert,’’ Trump said. ”I went down just to say hello to Melania, and while I was there I said hello to Putin.

“Really, pleasantries more than anything else. It was not a long conversation, but it was, you know, could be 15 minutes. Just talked about things,” Trump said. “Actually, it was very interesting; we talked about adoptions.”

It’s the same topic Trump’s oldest son, Donald Trump Jnr, says he discussed with a Russian lawyer at a meeting that has drawn intense scrutiny — a coincidence Trump described in the interview as “interesting”.